Several proposals have been made for apparatuses that float plate-shaped workpieces of a glass substrate and the like by gas ejection so far.
For example, Patent Literature 1 proposes a floatation suction mixture section 50 that is provided with a porous block 51 generating a positive pressure and a suction block 52 generating a negative pressure respectively on a base, as illustrated in FIG. 7(A). In the porous block 51, air is supplied, and the air is ejected from a top surface of a porous body to hold a plate-shaped workpiece 100 formed of a glass substrate in a noncontact state. At the same time, a suction force is worked in the suction block 52 to draw the glass substrate 100 to a top surface side of the floatation suction mixture section 50. By harmony of the suction force and the aforementioned floating force, the glass substrate 100 floats with a substantially fixed floating amount with respect to the top surface of the floatation suction mixture section 50, and a stable floating state is obtained.
Further, as illustrated in FIG. 8 (A), in Patent Literature 2, the plate-shaped workpiece 100 floated above a flotation device 60 is chucked and conveyed in arrow directions with a conveying device not illustrated. In the flotation device 60, air is ejected from entire surfaces of porous plates 61, and the entire surfaces of the porous plates 61 become air bearing surfaces, so that it becomes possible to float the plate-shaped workpiece 100 without causing a warp, and convey the plate-shaped workpiece 100 without contacting the porous plates 61. Further, in a suction hole 62, a force that sucks the plate-shaped workpiece 100 is generated. The suction force regulates a floatation amount of the plate-shaped workpiece 100 that is floated by the air ejected from the porous plate 61. Accordingly, by controlling the suction force, it becomes possible to control the floatation amount of the plate-shaped workpiece 100.